CN102446507B - Down-mixing signal generating and reducing method and device - Google Patents

Abstract

An embodiment of the present invention provides a method for generating a downmix signal, comprising: performing time-frequency transformation on the received left channel signal and right channel signal to obtain a frequency domain signal, dividing the frequency domain signal into several frequency bands; calculating The channel energy ratio and the channel phase difference of each frequency band; calculate the phase difference between the downmix signal and the first channel signal in each frequency band according to the channel energy ratio and the channel phase difference; according to the left channel signal, the right channel signal, the downmix signal and the phase difference of the first channel signal in each frequency band to calculate the frequency domain downmix signal. This method effectively improves the quality of stereo codec.

Description

A kind of lower mixed signal generates, the method and apparatus of reduction

Technical field

The present invention relates to stereo coding decoding field, be specifically related to the method and apparatus that a kind of lower mixed signal generates, reduces.

Background technology

In existing stereo encoding method, most methods all are to obtain a monophonic signal with mixed under the two-way sound channel signal of the left and right sides, and the sound field information of left and right acoustic channels is transmitted as sideband signals.The sound field information of left and right acoustic channels generally includes the energy Ratios of left and right acoustic channels, the phase differential of left and right acoustic channels, the simple crosscorrelation parameter of left and right acoustic channels, and the phase differential parameter of the first sound channel or second sound channel and lower mixed signal.Existing method is encoded these parameters and is sent to decoding end as side information, to recover stereophonic signal.

In these class methods, the sound field information extraction of lower mixing method, left and right acoustic channels and the synthetic core technology that all belongs to, industry also has many achievements in research at present.Existing stereo lower mixing method can be divided under the passive lower mixed active mixed two kinds.

Passive lower mixed algorithm is fairly simple, time-delay is lower, and the lower mixed factor is general to adopt 0.5 to calculate.

m(n)＝0.5·(x ₁(n)+x ₂(n))。

X wherein ₁(n), x ₂(n) represent respectively left channel signals, right-channel signals, the lower mixed signal of m (n) expression.

When fully anti-phase and amplitude was identical when left and right acoustic channels, lower mixed signal was 0, and decoding end has no idea to recover left and right sides two-way sound channel at all.Even not exclusively anti-phase, also can bring lower mixed signal energy disappearance.

In order to solve the lower mixed signal energy disappearance problem that passive algorithm causes, initiatively descend mixed algorithm at first left and right sides two paths of signals to be carried out time-frequency conversion, frequency domain adjust signal amplitude and or phase place, thereby the maximum energy of mixed signal under the maintenance.Below be an example of adjusting phase place:

At first left signal, right signal are carried out time-frequency conversion and obtain X ₁(k), X ₂(k), the phase differential in each subband of frequency-domain calculations; According to phase differential the right wing signal is carried out phase rotating again, obtain the signal behind the phase rotating

Phase place and the left road signal phase of right-channel signals are consistent after the rotation.After then according to following formula phase place being adjusted

With X ₁(k) the phase adduction multiply by the lower mixed signal that obtains frequency domain after 0.5,

Obtain at last the lower mixed signal of time domain by the time-frequency inverse transformation.This method can solve the anti-phase energy disappearance problem of left and right sound track signals.

But there is the faster lower mixcibility energy problem of stereophonic signal of the anti-phase and frequent saltus step of left and right acoustic channels and the other conversion of interchannel phase difference in existing lower mixing method, has reduced the subjective quality of stereo coding/decoding.

Summary of the invention

The method and apparatus that the embodiment of the invention provides a kind of lower mixed signal to generate, reduce is to improve the quality of stereo coding/decoding.

The embodiment of the invention provides a kind of generation method of lower mixed signal, and method comprises: left channel signals and right-channel signals are carried out time-frequency conversion obtain frequency-region signal, described frequency-region signal is divided into some frequency bands; Calculate channel energies ratio and the sound channel phase differential of each frequency band, described channel energies has been than having reflected left channel signals and the right-channel signals energy Ratios information at each frequency band, and described sound channel phase differential has reflected that left channel signals and right-channel signals are at the phase information of each frequency band; According to described channel energies than and the described lower mixed signal of described sound channel phase difference calculating and the first sound channel signal at the phase differential of each frequency band, described the first sound channel signal is described left channel signals or described right-channel signals; According to described left channel signals, right-channel signals and described lower mixed signal and the first sound channel signal mixed signal under the phase difference calculating frequency domain of each frequency band.

The embodiment of the invention provides the generating apparatus of time mixed signal, comprising: the time-frequency conversion unit, and be used for that the left channel signals that receives and right-channel signals are carried out time-frequency conversion and obtain frequency-region signal, described frequency-region signal is divided into some frequency bands; The frequency band computing unit, be used for calculating channel energies ratio and the sound channel phase differential of each frequency band, described channel energies has been than having reflected left channel signals and the right-channel signals energy Ratios information at each frequency band, and described sound channel phase differential has reflected that left channel signals and right-channel signals are at the phase information of each frequency band; The phase difference calculating unit, be used for according to channel energies than and the described lower mixed signal of sound channel phase difference calculating and the first sound channel signal at the phase differential of each frequency band, described the first sound channel signal is described left channel signals or described right-channel signals; Mixed signature computation unit under the frequency domain: lower mixed signature computation unit is used for according to described left channel signals, right-channel signals and described lower mixed signal and the first sound channel signal mixed signal under the phase difference calculating frequency domain of each frequency band.

The embodiment of the invention provides a kind of method of reducing of lower mixed signal, comprise: calculate the frequency-region signal amplitude of left channel signals, the frequency-region signal amplitude of right-channel signals according to the frequency-region signal amplitude of lower mixed signal, the channel energies that receives than respectively, described channel energies is than having reflected left channel signals and the right-channel signals energy Ratios information at each frequency band; According to the frequency-region signal phase place of described lower mixed signal, described channel energies than and the sound channel phase differential that receives calculate respectively the frequency-region signal phase place of left channel signals, the frequency-region signal phase place of right-channel signals, described sound channel phase differential has reflected that left channel signals and right-channel signals are at the phase information of each frequency band; According to the frequency-region signal amplitude of left channel signals, the frequency-region signal of the synthetic left channel signals of frequency-region signal phase place, according to the frequency-region signal amplitude of right-channel signals, the frequency-region signal of the synthetic right-channel signals of frequency-region signal phase place.

The embodiment of the invention provides a kind of reduction apparatus of lower mixed signal, it is characterized in that, comprise: the signal amplitude computing unit: be used for calculating the frequency-region signal amplitude of left channel signals, the frequency-region signal amplitude of right-channel signals according to the frequency-region signal amplitude of described lower mixed signal, the channel energies of reception than respectively, described sound channel amount is than having reflected left channel signals and the right-channel signals energy Ratios information at each frequency band; The signal phase computing unit: be used for according to the frequency-region signal phase place of described lower mixed signal, described channel energies than and the sound channel phase differential that receives calculate respectively the frequency-region signal phase place of left channel signals, the frequency-region signal phase place of right-channel signals, described sound channel phase differential has reflected that left channel signals and right-channel signals are at the phase information of each frequency band; Frequency-region signal computing unit: be used for the frequency-region signal amplitude according to left channel signals, the frequency-region signal of the synthetic left channel signals of frequency-region signal phase place, according to the frequency-region signal amplitude of right-channel signals, the frequency-region signal of the synthetic right-channel signals of frequency-region signal phase place.

The method and apparatus of the embodiment of the invention, the factor such as reduce that left and right acoustic channels is anti-phase, saltus step and the other conversion of interchannel phase difference are very fast to lower mixcibility can interference, effectively raise the quality of stereo coding/decoding.

Description of drawings

In order to be illustrated more clearly in the embodiment of the invention or technical scheme of the prior art, the below will do one to the accompanying drawing of required use in embodiment or the description of the Prior Art and introduce simply, obviously, accompanying drawing in the following describes is some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is the process flow diagram of an embodiment of the generation method of mixed signal under the present invention;

Fig. 2 is the structural drawing of an embodiment of the generating apparatus of mixed signal under the present invention;

Fig. 3 is the process flow diagram of an embodiment of the method for reducing of mixed signal under the present invention;

Fig. 4 is the structural drawing of an embodiment of the reduction apparatus of mixed signal under the present invention.

It will be appreciated by those skilled in the art that accompanying drawing is the synoptic diagram of a preferred embodiment, the module in the accompanying drawing or flow process might not be that enforcement the present invention is necessary.

Embodiment

For the purpose, technical scheme and the advantage that make the embodiment of the invention clearer, below in conjunction with the accompanying drawing in the embodiment of the invention, technical scheme in the embodiment of the invention is clearly and completely described, obviously, described embodiment is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, the every other embodiment that those of ordinary skills obtain under the prerequisite of not making creative work belongs to the scope of protection of the invention.

The embodiment of the invention provides a kind of generation method of lower mixed signal, and method comprises:

The left channel signals that receives and right-channel signals are carried out time-frequency conversion obtain frequency-region signal, described frequency-region signal is divided into some frequency bands;

Calculate the channel energies of each frequency band than (Channel Level Difference, CLD) and sound channel phase differential (Internal Phase Difference, IPD), described channel energies has been than having reflected left channel signals and the right-channel signals energy Ratios information at each frequency band, and described sound channel phase differential has reflected that left channel signals and right-channel signals are at the phase information of each frequency band;

According to mixed signal and the first sound channel signal are at the phase differential of each frequency band under channel energies ratio and the sound channel phase difference calculating, described the first sound channel signal is described left channel signals or described right-channel signals;

According to described left channel signals, right-channel signals, described lower mixed signal and the first sound channel signal mixed signal under the phase difference calculating frequency domain of each frequency band.

Please refer to accompanying drawing 1, Fig. 1 is the process flow diagram that is generated an embodiment of lower mixed signal method by left channel signals and right-channel signals, and step comprises:

S101 carries out time-frequency conversion to the left channel signals that receives and right-channel signals and obtains frequency-region signal, and described frequency-region signal is divided into some frequency bands;

S103 calculates channel energies ratio and the sound channel phase differential of each frequency band;

Mixed signal and the first sound channel signal were at the phase differential of each frequency band under S105 calculated;

S107 calculates mixed signal under the frequency domain.

S101 carries out time-frequency conversion to left channel signals and right-channel signals, in concrete implementation method, can use Fourier transform (Fourier Transform, FT), fast fourier transform (Fast Fourier Transform, the transform methods such as FFT), orthogonal mirror image conversion (Quadrature Mirror Filterbanks, QMF).Left channel signals and right-channel signals transform to frequency domain, obtain respectively L (k) and R (k).

Frequency-region signal is divided into some frequency bands, and in one embodiment of the invention, frequency span is 1.If k is the Frequency point index, b is band index, and kb is the initial frequency point index of b frequency band.

S103 calculates CLD and the IPD of each frequency band, comprises according to following formula calculating:

$\mathrm{CLD}\left(b\right)=10{\log }_{10}\frac{\underset{k=k_b}{\overset{k_{b+1}-1}{\mathrm{\Σ}}}{X}_1\left(k\right)X_1^{*}\left(k\right)}{\underset{k=k_b}{\overset{k_{b+1}-1}{\mathrm{\Σ}}}{X}_2\left(k\right)X_2^{*}\left(k\right)};$

IPD (b)=∠ cor (b), wherein $\mathrm{cor}\left(b\right)=\underset{k=k_b}{\overset{k=k_{b+1}-1}{\mathrm{\Σ}}}{X}_1\left(k\right)*X_2^{*}\left(k\right).$

Wherein, X1 (k) is left channel signals, and X2 (k) is right-channel signals.

Mixed signal and the first sound channel signal were at the phase differential of each frequency band under S105 calculated.

Embodiment 1: in one embodiment of the invention, the first sound channel is L channel.

Described lower mixed signal and left channel signals are calculated according to following formula at the phase differential of each frequency band:

$\mathrm{\θ}\left(b\right)=\frac{1}{1+c\left(b\right)}\·\mathrm{IPD}\left(b\right);$

C (b)=10 wherein ^{CLD (b) 10}

CLD (b) is the described channel energies ratio of b frequency band, c (b) is for the intermediate value variable that calculates, IPD (b) is the described sound channel phase differential of b frequency band, and θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

The left channel signals energy is larger, and the phase differential of described lower mixed signal and L channel is less; And when the R channel energy was larger, the phase differential of lower mixed signal and L channel was larger, and the phase differential of lower mixed signal and right channel is less.Lower mixed signal becomes positive relationship with the phase differential of L channel with the left channel signals energy, lower mixed signal becomes inverse relationship with the phase differential of L channel with the R channel energy, and lower mixed signal becomes positive relationship with the phase differential of L channel with the sound channel phase differential.

S107 calculates mixed signal under the frequency domain, and mixed signal calculates according to following formula under the described frequency domain:

$M_r\left(k\right)=0.5(1+\frac{R_{\mathrm{mag}}\left(k\right)}{L_{\mathrm{mag}}\left(k\right)})(L_r\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)+L_i\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right));$

$M_i\left(k\right)=0.5(1+\frac{R_{\mathrm{mag}}\left(k\right)}{L_{\mathrm{mag}}\left(k\right)})(L_i\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)-L_r\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right)).$

K is the Frequency point index, L _r(k) be the real part of k Frequency point of left channel signals time-frequency conversion, L _i(k) be the imaginary part of k Frequency point of left channel signals time-frequency conversion, R _Mag(k) be the amplitude of k Frequency point of right-channel signals time-frequency conversion, L _Mag(k) be the amplitude of k Frequency point of left channel signals time-frequency conversion, M _i(k) be the real part of k Frequency point of lower mixed signal time-frequency conversion, M _r(k) be the imaginary part of k Frequency point of lower mixed signal time-frequency conversion, θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

Embodiment 2: in another embodiment of the present invention, the first sound channel is R channel.

Described lower mixed signal and right-channel signals are calculated according to following formula at the phase differential of each frequency band:

$\mathrm{\θ}\left(b\right)=\frac{c\left(b\right)}{1+c\left(b\right)}\·\mathrm{IPD}\left(b\right);$

C (b)=10 wherein ^{CLD (b) 10}

CLD (b) is the described channel energies ratio of b frequency band, c (b) is for the intermediate value variable that calculates, IPD (b) is the described sound channel phase differential of b frequency band, and θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

The left channel signals energy is larger, and the phase differential of described lower mixed signal and R channel is larger, and the phase differential of lower mixed signal and L channel is less; And when the R channel energy was larger, the phase differential of lower mixed signal and R channel was less.Described lower mixed signal becomes inverse relationship with the phase differential of R channel with the energy of R channel, and described lower mixed signal becomes positive relationship with the phase differential of R channel with the energy of L channel, becomes positive relationship with described sound channel phase differential.

S107 calculates mixed signal under the frequency domain, and mixed signal calculates according to following formula under the described frequency domain:

$M_i\left(k\right)=0.5(1+\frac{L_{\mathrm{mag}}\left(k\right)}{R_{\mathrm{mag}}\left(k\right)})(R_i\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)-R_r\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right));$

$M_r\left(k\right)=0.5(1+\frac{L_{\mathrm{mag}}\left(k\right)}{R_{\mathrm{mag}}\left(k\right)})(R_r\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)+R_i\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right)).$

K is the Frequency point index, L _r(k) be the real part of k Frequency point of left channel signals time-frequency conversion, L _i(k) be the imaginary part of k Frequency point of left channel signals time-frequency conversion, R _Mag(k) be the amplitude of k Frequency point of right-channel signals time-frequency conversion, L _Mag(k) be the amplitude of k Frequency point of left channel signals time-frequency conversion, M _i(k) be the real part of k Frequency point of lower mixed signal time-frequency conversion, M _r(k) be the imaginary part of k Frequency point of lower mixed signal time-frequency conversion, θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

Embodiment 3: in another embodiment of the present invention, the first sound channel is the larger sound channel of signal amplitude in L channel and the R channel.

If the amplitude of left channel signals is greater than the amplitude of right-channel signals, the first sound channel is L channel, and the phase differential of the sound channel that signal amplitude is larger in lower mixed signal and described L channel and the R channel calculates according to following formula:

$\mathrm{\θ}\left(b\right)=\frac{1}{1+c\left(b\right)}\·\mathrm{IPD}\left(b\right);$

C (b)=10 wherein ^{CLD (b)/10}

S107 calculates mixed signal under the frequency domain, and mixed signal calculates according to following formula under the described frequency domain:

$M_r\left(k\right)=0.5(1+\frac{R_{\mathrm{mag}}\left(k\right)}{L_{\mathrm{mag}}\left(k\right)})(L_r\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)+L_i\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right));$

$M_i\left(k\right)=0.5(1+\frac{R_{\mathrm{mag}}\left(k\right)}{L_{\mathrm{mag}}\left(k\right)})(L_i\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)-L_r\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right)).$

K is the Frequency point index, L _r(k) be the real part of k Frequency point of left channel signals time-frequency conversion, L _i(k) be the imaginary part of k Frequency point of left channel signals time-frequency conversion, R _Mag(k) be the amplitude of k Frequency point of right-channel signals time-frequency conversion, L _Mag(k) be the amplitude of k Frequency point of left channel signals time-frequency conversion, M _i(k) be the real part of k Frequency point of lower mixed signal time-frequency conversion, M _r(k) be the imaginary part of k Frequency point of lower mixed signal time-frequency conversion, θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

If the amplitude of right-channel signals is greater than the amplitude of left channel signals, the first sound channel is R channel, and the phase differential of the sound channel that signal amplitude is larger in lower mixed signal and described L channel and the R channel calculates according to following formula:

$\mathrm{\θ}\left(b\right)=\frac{c\left(b\right)}{1+c\left(b\right)}\·\mathrm{IPD}\left(b\right);$

C (b)=10 wherein ^{CLD (b)/10}

S107 calculates mixed signal under the frequency domain, and mixed signal calculates according to following formula under the described frequency domain:

${;M}_i\left(k\right)=0.5(1+\frac{L_{\mathrm{mag}}\left(k\right)}{R_{\mathrm{mag}}\left(k\right)})(R_i\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)-R_r\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right))$

$M_r\left(k\right)=0.5(1+\frac{L_{\mathrm{mag}}\left(k\right)}{R_{\mathrm{mag}}\left(k\right)})(R_r\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)+R_i\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right)).$

K is the Frequency point index, L _r(k) be the real part of k Frequency point of left channel signals time-frequency conversion, L _i(k) be the imaginary part of k Frequency point of left channel signals time-frequency conversion, R _Mag(k) be the amplitude of k Frequency point of right-channel signals time-frequency conversion, L _Mag(k) be the amplitude of k Frequency point of left channel signals time-frequency conversion, M _i(k) be the real part of k Frequency point of lower mixed signal time-frequency conversion, M _r(k) be the imaginary part of k Frequency point of lower mixed signal time-frequency conversion, θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

The lower mixed signal creating method of the embodiment of the invention not only has the advantage of embodiment 1 and embodiment 2, can also effectively solve the problem of the stereo lower mixcibility energy of the very fast impact of small-signal phase tranformation.

Embodiment 4: among another embodiment of the present invention, described according to channel energies than and the sound channel phase difference calculating under mix signal and the phase differential of the first sound channel signal at each frequency band after, also comprise: the phase differential of described lower mixed signal and the first sound channel upgrades according to the faciation position, and the frequency domain envelope similarity of left channel signals and right-channel signals has been reflected in described faciation position.

In one embodiment of the invention, group's phase theta _gIt is the average of each frequency band IPD.

If the first sound channel is L channel: described lower mixed signal and left channel signals are calculated according to following formula at the phase differential of each frequency band:

$\mathrm{\θ}\left(b\right)=\frac{1}{1+c\left(b\right)}\·(\mathrm{IPD}\left(b\right)-{\mathrm{\θ}}_g);$

C (b)=10 wherein ^{CLD (b)/10}

CLD (b) is the described channel energies ratio of b frequency band, c (b) is for the intermediate value variable that calculates, IPD (b) is the described sound channel phase differential of b frequency band, and θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

The left channel signals energy is larger, and the phase differential of described lower mixed signal and L channel is less; And when the R channel energy was larger, the phase differential of lower mixed signal and R channel was less.

S107 calculates mixed signal under the frequency domain, and mixed signal calculates according to following formula under the described frequency domain:

$M_r\left(k\right)=0.5(1+\frac{R_{\mathrm{mag}}\left(k\right)}{L_{\mathrm{mag}}\left(k\right)})(L_r\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)+L_i\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right));$

$M_i\left(k\right)=0.5(1+\frac{R_{\mathrm{mag}}\left(k\right)}{L_{\mathrm{mag}}\left(k\right)})(L_i\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)-L_r\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right)).$

K is the Frequency point index, L _r(k) be the real part of k Frequency point of left channel signals time-frequency conversion, L _i(k) be the imaginary part of k Frequency point of left channel signals time-frequency conversion, R _Mag(k) be the amplitude of k Frequency point of right-channel signals time-frequency conversion, L _Mag(k) be the amplitude of k Frequency point of left channel signals time-frequency conversion, M _i(k) be the real part of k Frequency point of lower mixed signal time-frequency conversion, M _r(k) be the imaginary part of k Frequency point of lower mixed signal time-frequency conversion, θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

If the first sound channel is R channel, described lower mixed signal and right-channel signals are calculated according to following formula at the phase differential of each frequency band:

$\mathrm{\θ}\left(b\right)=\frac{c\left(b\right)}{1+c\left(b\right)}\·\mathrm{IPD}\left(b\right);$

C (b)=10 wherein ^{CLD (b)/10}

The left channel signals energy is larger, and the phase differential of described lower mixed signal and left channel signals is less; And when the R channel energy was larger, the phase differential of lower mixed signal and right-channel signals was less.

S107 calculates mixed signal under the frequency domain, and mixed signal calculates according to following formula under the described frequency domain:

$M_i\left(k\right)=0.5(1+\frac{L_{\mathrm{mag}}\left(k\right)}{R_{\mathrm{mag}}\left(k\right)})(R_i\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)-R_r\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right));$

$M_r\left(k\right)=0.5(1+\frac{L_{\mathrm{mag}}\left(k\right)}{R_{\mathrm{mag}}\left(k\right)})(R_r\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)+R_i\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right)).$

K is the Frequency point index, L _r(k) be the real part of k Frequency point of left channel signals time-frequency conversion, L _i(k) be the imaginary part of k Frequency point of left channel signals time-frequency conversion, R _Mag(k) be the amplitude of k Frequency point of right-channel signals time-frequency conversion, L _Mag(k) be the amplitude of k Frequency point of left channel signals time-frequency conversion, M _i(k) be the real part of k Frequency point of lower mixed signal time-frequency conversion, M _r(k) be the imaginary part of k Frequency point of lower mixed signal time-frequency conversion, θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

After the mixed signal, the method for the embodiment of the invention also comprises under described S107 calculating frequency domain:

Obtain mixed signal under the time domain of lower mixed signal by frequency-time domain transformation;

Obtain under the time domain the lower mixed monophony bit stream of mixed signal by the monophony scrambler, G.711.1 the monophony scrambler of the embodiment of the invention comprises ITU-T or G.722 waits.

When the frequency domain conversion of using in described monophony scrambler and the lower mixed signal is identical, can not need carries out frequency-time domain transformation and directly mixed signal under the frequency domain is encoded.

In order to keep coding side and decoding end CLD, the consistance of IPD, the embodiment of the invention adopts the CLD after quantizing, and IPD carries out lower mixed.The stereo parameter bit stream that CLD after the quantification, IPD obtain, and lower mixed monophony bit stream sends to decoding end in the lump.

The embodiment of the invention provides a kind of generating apparatus of lower mixed signal, comprising: 201 time-frequency conversion unit: be used for that the left channel signals that receives and right-channel signals are carried out time-frequency conversion and obtain frequency-region signal, described frequency-region signal is divided into some frequency bands; 203 frequency band computing units: the channel energies ratio and the sound channel phase differential that are used for calculating each frequency band, described channel energies has been than having reflected left channel signals and the right-channel signals energy Ratios information at each frequency band, and described sound channel phase differential has reflected that left channel signals and right-channel signals are at the phase information of each frequency band; 205 phase difference calculating unit: be used for according to channel energies than and the described lower mixed signal of sound channel phase difference calculating and the first sound channel signal at the phase differential of each frequency band, described the first sound channel signal is described left channel signals or described right-channel signals; Mixed signature computation unit under the frequency domain: 207 times mixed signature computation unit are used for according to described left channel signals, right-channel signals, described lower mixed signal and the first sound channel signal mixed signal under the phase difference calculating frequency domain of each frequency band.

Described 205 phase difference calculating unit be used for according to channel energies than and the described lower mixed signal of sound channel phase difference calculating and the first sound channel signal comprise at the phase differential of each frequency band: be used for according to channel energies compares and the described lower mixed signal of sound channel phase difference calculating and L channel and R channel signal amplitude the are larger sound channel signal phase differential at each frequency band.

When described the first sound channel is described L channel, described phase difference calculating unit be used for according to channel energies than and the described lower mixed signal of sound channel phase difference calculating and the first sound channel signal specifically comprise at the phase differential of each frequency band, according to following formula calculating:

c(b)＝10 ^CLD(b)/10；

$\mathrm{\θ}\left(b\right)=\frac{1}{1+c\left(b\right)}\·\mathrm{IPD}\left(b\right);$

Wherein, CLD (b) is the described channel energies ratio of b frequency band, c (b) is that IPD (b) is the described sound channel phase differential of b frequency band for the intermediate value variable that calculates, and θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

When the first sound channel was described R channel, described phase difference calculating unit was used for specifically comprising at the phase differential of each frequency band according to mixed signal and the first sound channel signal under channel energies ratio and the sound channel phase difference calculating, calculates according to following formula:

c(b)＝10 ^CLD(b)/10；

$\mathrm{\θ}\left(b\right)=\frac{c\left(b\right)}{1+c\left(b\right)}\·\mathrm{IPD}\left(b\right);$

CLD (b) is the described channel energies ratio of b frequency band, c (b) is for the intermediate value variable that calculates, IPD (b) is the described sound channel phase differential of b frequency band, and θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

Described phase difference calculating unit mixes signal and the phase differential of the first sound channel signal at each frequency band under being used for according to channel energies ratio and sound channel phase difference calculating after, also be used for: the phase differential of described lower mixed signal and the first sound channel is upgraded according to the faciation position, and the frequency domain envelope similarity of left channel signals and right-channel signals has been reflected in described faciation position.

When described the first sound channel is described L channel, described lower mixed signature computation unit, be used for specifically comprising according to described left channel signals, right-channel signals, described lower mixed signal and the first sound channel signal mixed signal under the phase difference calculating frequency domain of each frequency band, calculate according to following formula:

$M_r\left(k\right)=0.5(1+\frac{R_{\mathrm{mag}}\left(k\right)}{L_{\mathrm{mag}}\left(k\right)})(L_r\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)+L_i\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right));$

$M_i\left(k\right)=0.5(1+\frac{R_{\mathrm{mag}}\left(k\right)}{L_{\mathrm{mag}}\left(k\right)})(L_i\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)-L_r\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right)).$

K is the Frequency point index, L _r(k) be the real part of k Frequency point of left channel signals time-frequency conversion, L _i(k) be the imaginary part of k Frequency point of left channel signals time-frequency conversion, R _Mag(k) be the amplitude of k Frequency point of right-channel signals time-frequency conversion, L _Mag(k) be the amplitude of k Frequency point of left channel signals time-frequency conversion, M _i(k) be the real part of k Frequency point of lower mixed signal time-frequency conversion, M _r(k) be the imaginary part of k Frequency point of lower mixed signal time-frequency conversion, θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

When described the first sound channel is described R channel, describedly state lower mixed signature computation unit, be used for specifically comprising according to described left channel signals, right-channel signals, described lower mixed signal and the first sound channel signal mixed signal under the phase difference calculating frequency domain of each frequency band, calculate according to following formula:

$M_i\left(k\right)=0.5(1+\frac{L_{\mathrm{mag}}\left(k\right)}{R_{\mathrm{mag}}\left(k\right)})(R_i\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)-R_r\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right));$

$M_r\left(k\right)=0.5(1+\frac{L_{\mathrm{mag}}\left(k\right)}{R_{\mathrm{mag}}\left(k\right)})(R_r\left(k\right)\cos \left(\mathrm{\θ}\left(b\right)\right)+R_i\left(k\right)\sin \left(\mathrm{\θ}\left(b\right)\right));$

Wherein, k is the Frequency point index, R _r(k) be the real part of k Frequency point of right-channel signals time-frequency conversion, R _i(k) be the imaginary part of k Frequency point of right-channel signals time-frequency conversion, R _Mag(k) be the amplitude of k Frequency point of right-channel signals time-frequency conversion, L _Mag(k) be the amplitude of k Frequency point of left channel signals time-frequency conversion, M _i(k) be the real part of k Frequency point of lower mixed signal time-frequency conversion, M _r(k) be the imaginary part of k Frequency point of lower mixed signal time-frequency conversion, θ (b) is that described lower mixed signal and the first sound channel signal are at the phase differential of b frequency band.

The embodiment of the invention has proposed a kind of method of reducing of lower mixed signal, and as shown in Figure 3, Fig. 3 provides the process flow diagram of an embodiment of the inventive method, comprising:

S301 calculates respectively the frequency-region signal amplitude of left channel signals, the frequency-region signal amplitude of right-channel signals according to the frequency-region signal amplitude of described lower mixed signal, the channel energies ratio of reception;

S303 according to the channel energies of the frequency-region signal phase place of described lower mixed signal, reception than and the sound channel phase difference do not calculate the frequency-region signal phase place of left channel signals, the frequency-region signal phase place of right-channel signals, described sound channel phase differential has reflected that left channel signals and right-channel signals are at the phase information of each frequency band;

S305 is according to the frequency-region signal amplitude of left channel signals, the frequency-region signal of the synthetic left channel signals of frequency-region signal phase place, according to the frequency-region signal amplitude of right-channel signals, the frequency-region signal of the synthetic right-channel signals of frequency-region signal phase place.

In one embodiment of the invention, obtain lower mixed monophony time-domain signal by the mono decoder decoding, obtain stereo parameter CLD, IPD by the de-quantizer decoding.Lower mixed time-domain signal can obtain frequency-region signal by time-frequency conversion.

The channel energies of the described frequency-region signal amplitude according to described lower mixed signal of S301, reception is calculated the frequency-region signal amplitude of left channel signals than respectively, the frequency-region signal amplitude of right-channel signals specifically comprises, calculates according to following formula:

c(b)＝10 ^CLD(b)/10，

$\left|L\left(k\right)\right|=\frac{c\left(b\right)}{1+c\left(b\right)}\·\left|M\left(k\right)\right|,$

$\left|R\left(k\right)\right|=\frac{1}{1+c\left(b\right)}\·\left|M\left(k\right)\right|$

Wherein, k is the Frequency point index, CLD (b) is that described channel energies is than the channel energies ratio at b frequency band, c (b) is for the intermediate value variable that calculates, | M (k) | be that lower mixed signal M (k) is in the frequency-region signal amplitude of Frequency point k, | L (k) | be L channel road signal L (k) in the frequency-region signal amplitude of Frequency point k, | R (k) | be that right-channel signals R (k) is in the frequency-region signal amplitude of Frequency point k.

The described frequency-region signal phase place according to lower mixed signal of S303, channel energies than and the sound channel phase difference does not calculate the frequency-region signal phase place of left channel signals, the frequency-region signal phase place of right-channel signals specifically comprises, calculate according to following formula:

c(b)＝10 ^CLD(b)/10

$\∠L\left(k\right)=\∠M\left(k\right)+\frac{1}{1+c\left(b\right)}\·\mathrm{IPD}\left(b\right);$

$\∠R\left(k\right)=\∠M\left(k\right)-\frac{c\left(b\right)}{1+c\left(b\right)}\·\mathrm{IPD}\left(b\right)$

C (b) is for the intermediate value variable that calculates, IPD (b) is that described sound channel phase differential is at the sound channel phase differential of b frequency band, ∠ M (k) is that lower mixed signal M (k) is in the frequency-region signal phase place of Frequency point k, ∠ L (k) be left channel signals L (k) in the frequency-region signal phase place of Frequency point k, ∠ R (k) is that right-channel signals R (k) is in the frequency-region signal phase place of Frequency point k.

In one embodiment of the invention, the value of IPD (pi, pi].

Synthesize the frequency-region signal of left channel signals at S305 according to frequency-region signal amplitude, frequency-region signal phase place according to left channel signals, after the frequency-region signal according to the frequency-region signal amplitude of right-channel signals, the synthetic right-channel signals of frequency-region signal phase place, frequency-region signal obtains left and right acoustic channels time solution coded signal by frequency-time domain transformation.

The embodiment of the invention provides a kind of reduction apparatus of lower mixed signal, comprise: 401 signal amplitude computing units: be used for calculating the frequency-region signal amplitude of left channel signals, the frequency-region signal amplitude of right-channel signals according to the frequency-region signal amplitude of described lower mixed signal, the channel energies of reception than respectively, described sound channel amount is than having reflected left channel signals and the right-channel signals energy Ratios information at each frequency band; 403 signal phase computing units: the channel energies that is used for frequency-region signal phase place, reception according to described lower mixed signal than and the sound channel phase difference do not calculate the frequency-region signal phase place of left channel signals, the frequency-region signal phase place of right-channel signals, described sound channel phase differential has reflected that left channel signals and right-channel signals are at the phase information of each frequency band; 405 frequency-region signal synthesis units: be used for the frequency-region signal amplitude according to left channel signals, the frequency-region signal of the synthetic left channel signals of frequency-region signal phase place, according to the frequency-region signal amplitude of right-channel signals, the frequency-region signal of the synthetic right-channel signals of frequency-region signal phase place.

401 described signal amplitude computing units are used for that the channel energies of frequency-region signal amplitude, reception according to described lower mixed signal is calculated the frequency-region signal amplitude of left channel signals than respectively, the frequency-region signal amplitude of right-channel signals specifically comprises, according to following formula calculating:

c(b)＝10 ^CLD(b)/10，

$\left|L\left(k\right)\right|=\frac{c\left(b\right)}{1+c\left(b\right)}\·\left|M\left(k\right)\right|,$

$\left|R\left(k\right)\right|=\frac{1}{1+c\left(b\right)}\·\left|M\left(k\right)\right|$

Wherein, k is the Frequency point index, CLD (b) is that described channel energies is than the channel energies ratio at b frequency band, c (b) is for the intermediate value variable that calculates, | M (k) | be that lower mixed signal M (k) is in the frequency-region signal amplitude of Frequency point k, | L (k) | be L channel road signal L (k) in the frequency-region signal amplitude of Frequency point k, | R (k) | be that right-channel signals R (k) is in the frequency-region signal amplitude of Frequency point k.

403 described signal phase computing units are used for frequency-region signal phase place, the channel energies ratio according to lower mixed signal and the sound channel phase difference does not calculate the frequency-region signal phase place of left channel signals, the frequency-region signal phase place of right-channel signals specifically comprises, calculate according to following formula:

c(b)＝10 ^CLD(b)/10

$\∠L\left(k\right)=\∠M\left(k\right)+\frac{1}{1+c\left(b\right)}\·\mathrm{IPD}\left(b\right);$

$\∠R\left(k\right)=\∠M\left(k\right)-\frac{c\left(b\right)}{1+c\left(b\right)}\·\mathrm{IPD}\left(b\right)$

C (b) is for the intermediate value variable that calculates, IPD (b) is that described sound channel phase differential is at the sound channel phase differential of b frequency band, ∠ M (k) is that lower mixed signal M (k) is in the frequency-region signal phase place of Frequency point k, ∠ L (k) be left channel signals L (k) in the frequency-region signal phase place of Frequency point k, ∠ R (k) is that right-channel signals R (k) is in the frequency-region signal phase place of Frequency point k.

It will be appreciated by those skilled in the art that the module in the device among the embodiment can be distributed in the device of embodiment according to the embodiment description, also can carry out respective change and be arranged in the one or more devices that are different from present embodiment.The module of above-described embodiment can be merged into a module, also can further split into a plurality of submodules.

It should be noted that at last: above embodiment only in order to technical scheme of the present invention to be described, is not intended to limit; Although with reference to previous embodiment the present invention is had been described in detail, those of ordinary skill in the art is to be understood that: it still can be made amendment to the technical scheme that aforementioned each embodiment puts down in writing, and perhaps part technical characterictic wherein is equal to replacement; And these modifications or replacement do not make the essence of appropriate technical solution break away from the spirit and scope of various embodiments of the present invention technical scheme.

Claims (6)

1. A method for generating a downmix signal, characterized in that the method comprises: performing time-frequency transformation on the left channel signal and the right channel signal to obtain a frequency domain signal, and dividing the frequency domain signal into several frequency bands; Calculate the channel energy ratio and channel phase difference of each frequency band, the channel energy ratio reflects the energy ratio information of the left channel signal and the right channel signal in each frequency band, and the channel phase difference reflects the left channel phase difference Phase difference information of the channel signal and the right channel signal in each frequency band; Calculate the phase difference between the downmix signal and the first channel signal in each frequency band according to the channel energy ratio and the channel phase difference, where the first channel signal is the left channel signal or the Describe the right channel signal; calculating a frequency domain downmix signal according to the left channel signal, the right channel signal, and the phase difference between the downmix signal and the first channel signal in each frequency band; Wherein, the calculating the phase difference between the downmix signal and the first channel signal in each frequency band according to the channel energy ratio and the channel phase difference includes calculating according to the following formula: c(b)=10 ^CLD(b)/10 ,

Wherein, CLD(b) is the channel energy ratio of the bth frequency band, c(b) is an intermediate value variable used for calculation, IPD(b) is the channel phase difference of the bth frequency band, θ (b) is the phase difference between the downmix signal and the first channel signal in the b-th frequency band, the first channel is the left channel, and according to the left channel signal, the right channel The phase difference calculation of the signal, the downmix signal and the first channel signal in each frequency band The frequency domain downmix signal includes, calculated according to the following formula:

k is the frequency point index, L _r (k) is the real part of the kth frequency point of the time-frequency transformation of the left channel signal, L _i (k) is the imaginary part of the kth frequency point of the time-frequency transformation of the left channel signal, R _mag (k) is the amplitude of the kth frequency point of the time-frequency transformation of the right channel signal, L _mag (k) is the amplitude of the kth frequency point of the time-frequency transformation of the left channel signal, and M _i (k) is the downmix The real part of the kth frequency point of the signal time-frequency transformation, M _r (k) is the imaginary part of the kth frequency point of the time-frequency transformation of the downmixed signal, and θ(b) is the downmixed signal and the first channel signal the phase difference in the b-th frequency band; Alternatively, the calculating the phase difference between the downmix signal and the first channel signal in each frequency band according to the channel energy ratio and the channel phase difference includes calculating according to the following formula: c(b)=10 ^CLD(b)/10 ,

CLD(b) is the channel energy ratio of the bth frequency band, c(b) is an intermediate value variable used for calculation, IPD(b) is the channel phase difference of the bth frequency band, θ(b ) is the phase difference between the downmix signal and the first channel signal in the b frequency band, The first channel is the right channel, and the frequency domain is calculated according to the phase difference between the left channel signal, the right channel signal, the downmix signal and the first channel signal in each frequency band Mixed signals include, calculated according to the following formula:

Among them, k is the frequency point index, R _r (k) is the real part of the kth frequency point of the time-frequency transformation of the right channel signal, R _i (k) is the imaginary part of the kth frequency point of the time-frequency transformation of the right channel signal R _mag (k) is the amplitude of the kth frequency point of the time-frequency transformation of the right channel signal, L _mag (k) is the amplitude of the kth frequency point of the time-frequency transformation of the left channel signal, and M _i (k) is The real part of the kth frequency point of the time-frequency transformation of the downmixed signal, M _r (k) is the imaginary part of the kth frequency point of the time-frequency transformation of the downmixed signal, and θ(b) is the The phase difference of the channel signal in the b-th frequency band. 2. The method according to claim 1, wherein the first channel signal is a signal with a larger signal amplitude among the left channel signal and the right channel signal, and the energy ratio and The channel phase difference calculating the phase difference between the downmix signal and the first channel signal in each frequency band includes: calculating the downmix signal and the left channel signal, right channel signal according to the channel energy ratio and the channel phase difference The phase difference in each frequency band of the signal with greater signal amplitude in the channel signal. the 3. The method according to claim 1 or 2, wherein, after calculating the phase difference between the downmix signal and the first channel signal in each frequency band according to the channel energy ratio and the channel phase difference, further Including: the phase difference between the downmix signal and the first channel in each frequency band is updated according to the group phase, and the group phase reflects the frequency domain envelope similarity of the left channel signal and the right channel signal, according to the The left channel signal, the right channel signal, and the phase difference between the downmix signal and the first channel signal in each frequency band to calculate the frequency domain downmix signal includes: according to the left channel signal, the right channel signal, And the frequency-domain down-mix signal is calculated from the updated phase difference between the down-mix signal and the first channel signal in each frequency band. 4. A generating device for a downmix signal, comprising: a time-frequency conversion unit for performing time-frequency conversion on the received left channel signal and right channel signal to obtain a frequency domain signal, and converting the frequency domain signal to The signal is divided into several frequency bands; the frequency band calculation unit is used to calculate the channel energy ratio and channel phase difference of each frequency band, and the channel energy ratio reflects the energy of the left channel signal and the right channel signal in each frequency band Ratio information, the phase difference of the channel reflects the phase difference information of the left channel signal and the right channel signal in each frequency band; the phase difference calculation unit is used for according to the channel energy ratio and the channel phase difference Calculate the phase difference between the downmix signal and the first channel signal in each frequency band, the first channel signal is the left channel signal or the right channel signal; the downmix signal calculation unit is used for calculating a frequency-domain downmix signal according to the left channel signal, the right channel signal, and the phase difference between the downmix signal and the first channel signal in each frequency band; Wherein, the calculating the phase difference between the downmix signal and the first channel signal in each frequency band according to the channel energy ratio and the channel phase difference includes calculating according to the following formula: c(b)=10 ^CLD(b)/10 , Wherein, CLD(b) is the channel energy ratio of the bth frequency band, c(b) is an intermediate value variable used for calculation, IPD(b) is the channel phase difference of the bth frequency band, θ (b) is the phase difference between the downmix signal and the first channel signal in the b-th frequency band, The first channel is the left channel, and the frequency domain is calculated according to the phase difference between the left channel signal, the right channel signal, the downmix signal and the first channel signal in each frequency band Mixed signals include, calculated according to the following formula:

k is the frequency point index, L _r (k) is the real part of the kth frequency point of the time-frequency transformation of the left channel signal, L _i (k) is the imaginary part of the kth frequency point of the time-frequency transformation of the left channel signal, R _mag (k) is the amplitude of the kth frequency point of the time-frequency transformation of the right channel signal, L _mag (k) is the amplitude of the kth frequency point of the time-frequency transformation of the left channel signal, and M _i (k) is the downmix The real part of the kth frequency point of the signal time-frequency transformation, M _r (k) is the imaginary part of the kth frequency point of the time-frequency transformation of the downmixed signal, and θ(b) is the downmixed signal and the first channel signal the phase difference in the b-th frequency band; Alternatively, the calculating the phase difference between the downmix signal and the first channel signal in each frequency band according to the channel energy ratio and the channel phase difference includes calculating according to the following formula: c(b)=10 ^CLD(b)/10 ,

CLD(b) is the channel energy ratio of the bth frequency band, c(b) is an intermediate value variable used for calculation, IPD(b) is the channel phase difference of the bth frequency band, θ(b ) is the phase difference between the downmix signal and the first channel signal in the b-th frequency band, The first channel is the right channel, and the frequency domain is calculated according to the phase difference between the left channel signal, the right channel signal, the downmix signal and the first channel signal in each frequency band Mixed signals include, calculated according to the following formula:

Among them, k is the frequency point index, R _r (k) is the real part of the kth frequency point of the time-frequency transformation of the right channel signal, R _i (k) is the imaginary part of the kth frequency point of the time-frequency transformation of the right channel signal R _mag (k) is the amplitude of the kth frequency point of the time-frequency transformation of the right channel signal, L _mag (k) is the amplitude of the kth frequency point of the time-frequency transformation of the left channel signal, and M _i (k) is The real part of the kth frequency point of the time-frequency transformation of the downmixed signal, M _r (k) is the imaginary part of the kth frequency point of the time-frequency transformation of the downmixed signal, θ(b) is the The phase difference of the channel signal in the b-th frequency band. 5. The device according to claim 4, wherein the phase difference calculation unit is used to calculate the downmix signal and the left channel signal, the right channel signal, and the right channel signal according to the channel energy ratio and the channel phase difference. The phase difference in each frequency band of the channel signal with larger amplitude among the channel signals. 6. The device according to claim 4 or 5, wherein the phase difference calculation unit is used to calculate the downmix signal and the first channel signal in each frequency band according to the channel energy ratio and the channel phase difference After the phase difference of , it is also used to: update the phase difference between the downmix signal and the first channel according to the group phase, the group phase reflects the frequency domain envelope similarity of the left channel signal and the right channel signal . the

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